The bioelectrical interactions and activity believed to be present in a variety of biological tissues and cells are one of the least understood of the physiological processes. However, there has recently been much research into these interactions and activity regarding the growth and repair of certain tissues and cells. In particular, there has been much research into stimulation by electric and electromagnetic fields and its effect on the growth and repair of bone, cartilage, and various growth factors. Researchers believe that such research may be useful in the development of new treatments for a variety of medical problems.
Transforming growth factor—beta (TGF-β) is a pleiotropic growth factor that is present in most tissues and is implicated in cell proliferation, migration, differentiation, and survival. Consequently, TGF-β has clinical applications in diverse conditions such as angiogenesis, autoimmunity, bone repair (fractures, delayed unions, nonunions) and bone maintenance (osteoporosis), cartilage maintenance (degenerative arthritis), tumor suppression, and wound healing (Kim et al., J of Biochemistry and Molecular Biology, 38: 1-8, (2005); Janssens et al., Endocrine Reviews, 26: 743-774, (2005).
In acute fractures, delayed union and nonunion of fractures, and in various defects of bone, the formation of new, healing bone is dependent upon the presence of bone morphogenetic proteins (BMPs) to induce bone formation and TGF-βs to induce cartilage formation. In PCT Patent Application Serial No. PCT/US2005/00793, filed Jan. 11, 2005 (claiming priority from U.S. Provisional Patent Application No. 60/535,755, filed Jan. 12, 2004), it was shown that the gene expression of BMPs could be up-regulated by specific and selective electric and electromagnetic fields for the treatment of injured or diseased bone. It is shown herein that the gene expression of TGF-βs can also be up-regulated by specific and selected electric and electromagnetic fields. It is also shown herein that the optimal signal for the gene expression of BMPs is slightly different from that of TGF-βs, and this difference allows one to design a device that delivers one signal that maximally up-regulates the BMPs during the bone phase of fracture healing and another signal that primarily up-regulates the TGF-βs during the cartilage phase of fracture healing. This would be very useful in fracture healing, for instance, where the fracture callus is initially composed of cartilage that gradually is replaced by bone. By maximally up-regulating the TGF-βs to form cartilage early in the healing process, and maximally up-regulating the BMPs to form bone later in the healing process, one is able to optimize the healing of acute fractures, accelerate the healing in delayed fracture healing, and restart the healing process in nonunion fractures.
Up-regulation of TGF-β may also be useful in the treatment of the disease commonly known as osteoporosis, where bone demineralizes and becomes abnormally rarefied. Bone comprises an organic component of cells and matrix as well as an inorganic or mineral component. The cells and matrix comprise a framework of collagenous fibers that is impregnated with the mineral component of calcium phosphate (85%) and calcium carbonate (10%) that imparts rigidity to the bone. In healthy bone, bone formation and bone resorption are in balance. In osteoporosis, bone resorption exceeds bone formation, leading to bone weakening and possible vertebral body fracture and collapse. While osteoporosis is generally thought as afflicting the elderly, certain types of osteoporosis may affect persons of all ages whose bones are not subject to functional stress. In such cases, patients may experience a significant loss of cortical and cancellous bone during prolonged periods of immobilization. Elderly patients are known to experience bone loss due to disuse when immobilized after fracture of a bone, and such bone loss may ultimately lead to a secondary fracture in an already osteoporotic skeleton. Diminished bone density may lead not only to vertebrae collapse, but also to fractures of hips, lower arms, wrists, ankles as well as incapacitating pains. Alternative non-surgical therapies for such diseases are needed.
Pulsed electromagnetic fields (PEMF) and capacitive coupling (CC) have been used widely to treat nonhealing fractures (nonunion) and related problems in bone healing since approval by the Food and Drug Administration in 1979. The original basis for the trial of this form of therapy was the observation that physical stress on bone causes the appearance of tiny electric currents that, along with mechanical strain, were thought to be the mechanisms underlying transduction of the physical stresses into a signal that promotes bone formation. Along with direct electric field stimulation that was successful in the treatment of nonunion, noninvasive technologies using PEMF and capacitive coupling (where the electrodes are placed on the skin in the treatment zone) were also found to be effective. PEMFs generate small, induced currents (Faraday currents) in the highly-conductive extracellular fluid, while capacitive coupling directly causes currents in the tissues; both PEMFs and CC thereby mimic endogenous electrical currents.
The endogenous electrical currents, originally thought to be due to phenomena occurring at the surface of crystals in the bone, have been shown to be due primarily to movement of fluid containing electrolytes in channels of the bone containing organic constituents with fixed negative charges, generating what are called “streaming potentials.” Studies of electrical phenomena in bone have demonstrated a mechanical-electrical transduction mechanism that appears when bone is mechanically compressed, causing movement of fluid and electrolytes over the surface of fixed negative charges in the proteoglycans and collagen in the bone matrix. These streaming potentials serve a purpose in bone, and, along with mechanical strain, lead to signal transduction that is capable of stimulating bone cell synthesis of a calcifiable matrix, and, hence, the formation of bone.
The main application of direct current, capacitive coupling, and PEMFs has been in orthopedics in healing of nonunion bone fractures (Brighton et al., J. Bone Joint Surg. 63: 2-13, 1981; Brighton and Pollack, J. Bone Joint Surg. 67: 577-585, 1985; Bassett et al., Crit. Rev. Biomed. Eng. 17: 451-529, 1989; Bassett et al., JAMA 247: 623-628, 1982). Clinical responses have been reported in avascular necrosis of hips in adults and Legg-Perthes's disease in children (Bassett et al., Clin. Orthop. 246: 172-176, 1989; Aaron et al., Clin. Orthop. 249: 209-218, 1989; Harrison et al., J. Pediatr. Orthop. 4: 579-584, 1984). It has also been shown that PEMFs (Mooney, Spine 15: 708-712, 1990) and capacitive coupling (Goodwin, Brighton et al., Spine 24: 1349-1356, 1999) can significantly increase the success rate of lumbar fusions. There are also reports of augmentation of peripheral nerve regeneration and function and promotion of angiogenesis (Bassett, Bioessays 6: 36-42, 1987). Patients with persistent rotator cuff tendonitis refractory to steroid injection and other conventional measures, showed significant benefit compared with placebo-treated patients (Binder et al., Lancet 695-698, 1984). Finally, Brighton et al. have shown in rats the ability of an appropriate capacitive coupling electric field to both prevent and reverse vertebral osteoporosis in the lumbar spine (Brighton et al., J. Orthop. Res. 6: 676-684, 1988; Brighton et al., J. Bone Joint Surg. 71: 228-236, 1989).
More recently, research in this area has focused on the effects stimulation has on tissues and cells. For example, it has been conjectured that direct currents do not penetrate cellular membranes, and that control is achieved via extracellular matrix differentiation (Grodzinsky, Crit. Rev. Biomed. Eng. 9:133-199, 1983). In contrast to direct currents, it has been reported that PEMFs can penetrate cell membranes and either stimulate them or directly affect intracellular organelles. An examination of the effect of PEMFs on extracellular matrices and in vivo endochondral ossification found increased synthesis of cartilage molecules and maturation of bone trabeculae (Aaron et al., J. Bone Miner. Res. 4: 227-233, 1989). More recently, Lorich et al. (Clin. Orthop. Related Res. 350: 246-256, 1998) and Brighton et al. (J. Bone Joint Surg. 83-A, 1514-1523, 2001) reported that signal transduction of a capacitively coupled electric signal is via voltage gated calcium channels, whereas signal transduction of PEMFs or combined electromagnetic fields is via the release of calcium from intracellular stores. In all three types of electrical stimulation there is an increase in cytosolic calcium with a subsequent increase in activated (cytoskeletal) calmodulin.
It was reported in 1996 by the present inventors that a cyclic biaxial 0.17% mechanical strain produces a significant increase in TGF-β1 mRNA in cultured MC3T3-E1 bone cells in a cooper dish (Brighton et al., Biochem. Biophys. Res. Commun. 229: 449-453, 1996). Several significant studies followed in 1997. In one study it was reported that the same cyclic biaxial 0.17% mechanical strain produced a significant increase in PDGF-A mRNA in similar bone cells (Brighton et al., Biochem. Biophys. Res. Commun. 43: 339-346, 1997). It was also reported that a 60 kHz capacitively coupled electric field of 20 mV/cm produced a significant increase in TGF-β1 in similar bone cells in a cooper dish (Brighton et al., Biochem. Biophys. Res. Commun. 237: 225-229, 1997). However, the effect such a field would have on other genes within the body has not been reported in the literature.
In the above-referenced parent patent application, entitled Regulation of Genes Via Application of Specific and Selective Electrical and Electromagnetic Signals, methods were disclosed for determining the specific and selective electrical and electromagnetic signals for use in creating fields for regulating target genes of diseased or injured tissues. The present invention builds upon the technique described therein by describing the method of regulating expression of one targeted gene family, namely, TGF-β's gene expression, through application of a field generated by a specific and selective electrical and electromagnetic signal, for the treatment of fresh fractures, fractures at risk, delayed unions, nonunion of fractures, bone defects, spine fusions, osteonecrosis or avascular necrosis, as an adjunct to other therapies in the treatment of one or all of the above, and in the treatment of osteoporosis.